1. Field of the Invention
The present invention is in the field of transconductance amplifiers for amplifying or attenuating analog signals.
2. Description of the Related Art
A transconductance amplifier converts a voltage signal to a current signal as linearly as possible, with the output forming as ideal a current source as possible. Such transconductance amplifiers are used to advantage instead of voltage amplifiers where analog signals are to be amplified or attenuated, e.g., for continuous or step-by-step gain control. Another application is the implementation of switchover and switch-off functions, which is easier with currents than with voltages. In that case, transconductance amplifiers are preceded by analog multipliers which have a current-dividing network and are controlled by a control signal, which becomes a switching signal in an extreme case.
A further application of transconductance amplifiers is in the implementation of integrators. As a rule, currents are integrated there by means of a capacitor, i.e., the voltage signals to be integrated first have to be converted into current signals.
The dynamic range of conventional transconductance amplifiers is determined by the value of the quiescent current, which is usually at the center of the dynamic range. Under overload conditions, the output current is limited at the overload level by twice the value of the quiescent current and at the minimum acceptable signal level by the current which has become zero. This limiting results in nonlinear distortion, which is caused by odd harmonics.